OCT is a method of creating an optical coherence tomographic image that allows a precise tomographic image of the inside of a subject body to be obtained. OCT uses light reflected back from parts of the subject body in response to low-coherence light laterally emitted from the distal end of an optical probe inserted into an organ of the patient such as a blood vessel or the bowels. A basic technology of the OCT is disclosed in Japanese Examined Patent Application Publication No. 6-35946 (Patent Literature 1), and specific structures of the optical probes are disclosed in Japanese Unexamined Patent Application Publication No. 11-56786 (Patent Literature 2), Japanese Unexamined Patent Application Publication No. 2008-200283 (Patent Literature 3), and so forth.
FIG. 18 is a sectional explanatory view of a related-art lateral light emitting device (optical probe) described in Patent Literatures 2 and 3.
A distal end holding portion 11 is mounted at a distal end of a cylindrical shaft 10, a distal end of an optical fiber 2 that is inserted through the shaft 10 is engaged with a proximal end side of the distal end holding portion 11, and a rod lens 3, to which a prism 4 is bonded, is engaged with a distal end of the distal end holding portion 11. The entirety of the lateral light emitting device is covered with a transparent sheath 12 in order to prevent the subject body from being damaged and prevent the prism 4 and the rod lens 3 from becoming completely detached and being left inside the subject body.